I. Field of the Invention
This invention deals with the shaping of heated glass sheets and, more particularly, to forming compound curvatures in glass sheets by roll forming.
II. Discussion of the Technology
Often times in the commercial usage of glass, a glass sheet must be formed in configurations having various curvatures. As used herein, the curvature of glass in its short dimension is referred to as its transverse curvature, while curvature in its longitudinal direction is referred to as its longitudinal curvature. Transverse curvature is measured in a plane passing through the glass in its transverse direction and perpendicular to the glass surface. Longitudinal curvature is measured in a vertical plane along a longitudinal direction of the glass. It follows that if the transverse or longitudinal curvature is constant, the curvature of the glass is essentially along the arc of the circle having a given radius of curvature.
The curvature of a flat glass sheet is manipulated during forming to provide the desired shape and configuration. In roll forming, the glass sheet is deformed by gravity to assume a transverse and/or longitudinal curvature. The transverse curvature is formed by using curved transverse forming rolls. Longitudinal curvature is formed by mounting the individual rolls at the exit end of the heating furnace along a constant longitudinally extending arc. Due to the geometry of the roll forming arrangement, the resulting glass has both a constant transverse curvature in the longitudinal direction of the glass sheet and constant longitudinal curvature in the transverse direction of the glass sheet.
The present invention provides an apparatus and method of forming a glass sheet with a roll forming apparatus so that the glass sheet has a longitudinal radius of curvature that varies in the transverse direction of the glass sheet without replacing the transverse forming rolls.